[From Burke's Peerage-see source for details]An undoubted Earl of Gloucester, perhaps the first authentic one, at any rate after the Conquest, is Robert FitzHamon's son-in-law, another Robert, who was an illegitimate son of Henry I and was so created 1122. The Earldom passed to his eldest son, William FitzRobert, and from him to John, later King John andhusband from 1189 to 1199 (when he divorced her) of Isabel, the youngest of William FitzRobert's three daughters. On John's coming to the throne the title did not merge in the Crown for it was not his in his own right but in right of his wife.